The present invention relates to devices known under the title "automatic distribution units", meaning devices serving the purpose of supplying a pipe with a fluid at a particular pressure coming from two vessels, of which one is operative whilst the other is on standby. These devices commonly comprise distributor means arranged to place one or the other of the two vessels in communication with the said pipe, means for switching the distributor means sensitive to the degree of filling of the vessel in operation, and pressure regulator means delivering the fluid under the utilisation pressure.
In known devices of this kind, intended for supplying gas from two high-pressure bottles, the distributor means and their switching means are combined into a mechanical apparatus comprising a slide valve submitted to two opposed pressures. An arrangement of this nature necessitates the installation of pressure regulator means upstream of this apparatus, which leads to a definite number of disadvantages. In particular:
the reliability of the switching operation is not absolute, since switchover depends on very small pressure differences, which may experience difficulties in overcoming mechanical resistances, for example those of friction sealing joints,
for the same reason, it is difficult to govern the switching pressure and the delivery pressure is not perfectly stable during reversing actions,
whilst one vessel is on standby, the pressure regulator allocated to this vessel remains idle, without gaseous scavenging. This may raise problems during reversing actions, particularly in the case of a corrosive gas.
The invention has as its object to provide an automatic unit which is completely reliable, controllable with precision and able to assure a stable pressure during reverse switching actions.